gistfile1.java

public class ANewlyCreatedRpnCalculatorShould {

  private RpnCalculator calculator;

  @Before 
  public void init(){
    calculator = new RpnCalculator();
  }

  @Test
  public void Have0InItsAccumulator(){ ... }

  @Test
  public void AllowItsAccumulatorToBeSet(){ ... }

  @Test
  public void AllowMultipleValuesToBeStored(){
    BigDecimal value = new BigDecimal(42);
    BigDecimal value2 = new BigDecimal(2);
    BigDecimal value3 = new BigDecimal(3);
    calculator.setAccumulator(value);
    calculator.enter();
    calculator.setAccumulator(value2);
    calculator.enter();
    calculator.setAccumulator(value3);
    assertEquals(value3, calculator.getAccumulator());
    calculator.drop();
    assertEquals(value2, calculator.getAccumulator());
    calculator.drop();
    assertEquals(value, calculator.getAccumulator());
  }

}

gistfile2.java

public class ACalculatorWithThreeValuesShould{

  private RpnCalculator calculator;
  BigDecimal value = new BigDecimal(42);
  BigDecimal value2 = new BigDecimal(2);
  BigDecimal value3 = new BigDecimal(3);

  @Before 
  public void init(){
    calculator = new RpnCalculator();
    calculator.setAccumulator(value);
    calculator.enter();
    calculator.setAccumulator(value2);
    calculator.enter();
    calculator.setAccumulator(value3);
  }

  @Test
  public void HaveTheLastValueEnteredInItsAccumulator(){
    assertEquals(value3, calculator.getAccumulator());
  }

  @Test
  public void HaveTheSecondToLastValueAfterASingleDrop(){
    calculator.drop();
    assertEquals(value2, calculator.getAccumulator());
  }

  @Test
  public void HaveTheFirstValueEnteredAfterTwoDrops(){
    calculator.drop();
    calculator.drop();
    assertEquals(value, calculator.getAccumulator());
  }

  @Test
  public void Have0AfterThreeDrops(){
    calculator.drop();
    calculator.drop();
    calculator.drop();
    assertEquals(BigDecimal.ZERO, calculator.getAccumulator());
  }


}